Kinetic Modeling of n-Butane Cracking on HZSM-5 Zeolite Catalyst

Abstract

A kinetic model of lumps has been established for n-butane cracking over HZSM-5 zeolite catalyst (SiO2/Al2O3 = 30) in the 400−550 °C range, based on the results obtained in a fixed bed reactor (space time, up to 2.4 (g of catalyst) h (mol CH2)−1; He/n-butane molar ratio in the feed, up to 6/1; time on stream, 5 h). The model allows quantifying the distribution of the lumps of products (C2−C4 olefins, C2−C4 paraffins, methane, and C5−C10 components) in a wide range of temperatures, partial pressures of hydrocarbons in the reaction medium, and space times. The kinetic model steps for the transformation of n-butane into olefins and of olefins into paraffins and C5−C10 are second order with respect to the reactant, whereas the remaining steps are first order with respect to each reactant. When the target is the production of C2−C4 olefins, the yield is limited to 12%, at 550 °C.

Olefin production by cofeeding methanol and n‐butane: Kinetic modeling considering the deactivation of HZSM‐5 zeolite

“…However, isobutane yield decreases to 10% for high-values of space time, with propane being the main paraffin (74% of paraffin lump), which is a similar result to that corresponding to n-butane cracking. 33 The yield of C 5þ aliphatic fraction peaks similarly as observed for C 2 AC 4 olefins, due its prevailing content of C 5þ olefins. The yield of this fraction, like that corresponding to aromatics and methane, tends to a constant pseudoequilibrium value.…”

“…The hypotheses for the kinetic modeling are based on the kinetic models previously established for each of the two reactions on the same catalyst. 33,34 Experimental Reaction equipment and product analysis…”

“…Similarly to n-butane cracking, 33 only the yield of paraffins and aromatics are affected by catalyst deactivation for higher-values of space time (Figure 8 corresponding to 9.5 (g of catalyst) h (mol CH 2 ) À1 ), whereas the yield of the remaining reaction products remains almost constant for 5 h.…”

“…33 Kinetic modeling for zero time on stream Figure 9 shows the kinetic scheme corresponding to the best fit to the experimental results. The kinetic equations for the formation of each component or lump corresponding to this scheme are as follow…”

Nine-Lump Kinetic Study of Catalytic Pyrolysis of Gas Oils Derived from Canadian Synthetic Crude Oil

“…Several lumping kinetic models are available for the catalytic pyrolysis of propane [25], 4 hydrocarbons [26,27], naphtha [28], gas oils [16,29], and heavy oils [30][31][32]. These studies can be used as references in the kinetic study of the catalytic pyrolysis of gas oils.…”